This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 74 |
| 5 | 276 |
| 6 | 1044 |
| 7 | 3992 |
| 8 | 15414 |
| 9 | 59948 |
| 10 | 234484 |
| 11 | 921432 |
| 12 | 3634916 |
| 13 | 14386248 |
| 14 | 57097704 |
| 15 | 227166384 |
| 16 | 905714150 |
| 17 | 3617851980 |
| 18 | 14475452484 |
| 19 | 58004111160 |
| 20 | 232737175404 |
| 21 | 934969613528 |
| 22 | 3760157234584 |
| 23 | 15137340947280 |
| 24 | 60994657996476 |
| 25 | 245980435701752 |